1. Field of the Invention
The use of Calcium (Hexa)Aluminate as an aggregate in shapes and castables for use as a chemical barrier and/or a refractory for high alkali/alkaline environments. The present invention provides a method of using an improved aggregate based on CaO.6(Al2O3) (hereinafter referred to as calcium hexa aluminate, “CA6”, or “CA6”, all of which are interchangeable and equivalent terms as used herein) and analogs or derivatives thereof including those based on barium substitution for calcium or barium additions resulting in calcium substitution after chemical reaction and/or heat treatment, all of which are referred to herein as CA6. Methods of using the chemical barriers and/or refractory materials based on aggregate compositions having these phases singularly or combined are provided in the present invention.
2. Description of the Background Art
U.S. Patent Application Publication No. U.S. 2005/0049138 A1 (Publication Date Mar. 3, 2005) entitled “Calcium Aluminate Clinker as a Refractory Aggregate With and Without Barium Addition and Use Thereof” teaches an improved refractory aggregate composition based on CaO.Al2O3 clinker (hereinafter referred to as “CA” clinker and designated by the following equation CnAx, wherein n is an integer from about 1 to 12 and x is an integer from about 1-24, and wherein the clinker has from zero to less than 50 weight percent C12A7, and wherein greater than 98 weight percent of the clinker has a particle size ranging from 325 mesh (45 microns) to +10 mesh (+2 mm)) and CnAx hydrate phases and analogs or derivatives thereof including those based on barium substitution for calcium or barium additions resulting in calcium substitution after chemical reaction and/or heat treatment, all of which are referred to herein as CA clinker. Methods of using refractory materials or chemical barriers based on aggregate compositions having these phases singularly or combined, and exclusive of C12A7 as a major phase, are provided. More specifically, this art discloses a refractory composition comprising a refractory aggregate consisting essentially of CA6 and a method for improving the insulating character and/or penetration resistance of a liner in contact with molten aluminum in the aluminum industry.
J. E. Kopanda and G. MacZura, Aluminum Company of America, “Production Processes, Properties, and Applications for Calcium Aluminate Cements”, Alumina Chemical Science and Technology Handbook, Am. Ceramic Sci., pages 171-183 (1990), describes the historical development of calcium aluminate cements, the raw materials used in the manufacturing process, and the chemical and physical properties, and the hydration/dehydration reactions associated therewith.
An area not discussed in the background art is a method of using a composition comprising CA6 as a refractory aggregate or chemical barrier in high alkali or high alkaline environments.